An automotive electric compressor is generally installed in a vehicle, such as an electric vehicle (EV), a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (PHEV), and a fuel cell electric vehicle (FCEV).
In Patent Document 1, an electric compressor is disclosed that is provided with a power converter (an inverter) for converting a direct current (DC) voltage applied from an external source to a three-phase alternating current (AC) power, a motor for rotating a compressor using the three-phase AC power, and a compressor for compressing a coolant.
The type of DC voltage described in Patent Document 1 is supplied from a high voltage battery installed in the above-described vehicle, or from a DC/DC converter connected to the high voltage battery.
Although the range of the DC voltage varies depending on the type of the vehicle, many of the above-described vehicles, such as the EV, generally have a 300 V system (from 150 V to 450 V), which is a high voltage system. The current capacity of the DC voltage of the 300 V system is at most around 30 A in general. Thus, the size of an energized member also does not increase due to a relationship between the current and the temperature, so the electric compressor can be designed in a relatively compact manner.
In addition, with respect to engine vehicles also, environmental considerations, such as performing idling stop and the like, will become increasingly important. Thus, a demand for the electric compressor will be heightened, even for engine vehicles that are not provided with the high voltage battery.
However, the main purpose of a battery installed in the engine vehicle is to drive a control device, so the battery only supplies a low voltage, such as 12 V or 24 V. Note that, although the voltage of the battery may be increased up to approximately 50 V as a result of an increase in the number of installed electrical components, it is thought that only a few engine vehicle models will adopt a high voltage system as high as the 300 V system installed in the EV and the like.
Then, if an electric compressor having substantially the same capability as the 300 V system is driven by a 12 V low voltage system (12 V to 50 V), the energizing current is increased to approximately 300 A, which is approximately 10 times higher than the current used when the electric compressor is driven by the 300 V system. When an inverter of the electric compressor is configured while taking this into account, the cross-sectional area of the energized member needs to be increased to approximately 10 times that of a conventional energized member, since the temperature increases as a result of the increase in the current. As a result, the inverter of the electric compressor increases in size, and the inverter is not easily installed in an engine room or the like of the vehicle. Further, if an electric compressor is newly designed to be used with the 12 V system, design resources of the electric compressor using the 300 V system cannot be used, resulting in an increase in costs.
Thus, in Patent Document 2, an automotive electric compressor is disclosed that is provided with a boost converter that boosts a DC voltage output from a low voltage DC power supply to a high voltage and that uses the boosted DC voltage after converting the boosted DC voltage to AC voltage.